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Abstract:

Disclosed is a differential pressure valve comprising: a valve body, the
valve body having at least one flow inlet and one flow outlet: at least
one shutter, the shutter being movable between an open position and a
closed position under a differential pressure across the valve; at least
one flow passage from the flow inlet to the flow outlet; at least one
biasing member configured to bias the shutter towards a closed position
so as to block the flow passage through the flow inlet. The biasing
member is a non-linear biasing member.

Claims:

1. A differential pressure valve comprising: a valve body, the valve body
having at least one flow inlet and one flow outlet; at least one shutter,
the shutter being movable between an open position and a closed position
under a differential pressure across the valve; at least one flow passage
from the flow inlet to the flow outlet; at least one biasing member
configured to bias the shutter towards a closed position so as to block
the flow passage through the flow inlet, wherein the biasing member is
non-linear.

2. The valve according to claim 1, wherein the biasing member comprises a
non-linear helical spring.

3. The valve according to claim 1, wherein the biasing member comprises a
first non-linear helical spring and a second helical spring arranged in
parallel.

4. The valve according to claim 3, wherein the second helical spring is
non-linear.

5. The valve according to claim 3, wherein the first non-linear helical
spring and the second non-linear helical spring are arranged coaxially to
one another and one inside the other.

6. The valve according to claim 1, wherein the biasing member comprises a
ring spring provided with a plurality of coaxial conical faced inner and
outer ring elements assembled in a columnar form.

7. The valve according to claim 6, wherein at least two of the ring
elements have different stiffness.

8. The valve according to claim 1, wherein the biasing member comprises a
plurality of coaxially arranged Belleville springs.

9. The valve according to claim 8, wherein at least two of the Belleville
springs have different stiffness.

10. The valve according to claim 8, wherein spacer rings of differing
height are arranged between consecutive Belleville springs.

11. The valve according to claim 1, wherein the biasing member is
constructed and arranged such that the stiffness thereof increases as the
deflection increases.

12. The valve according to claim 11, wherein the biasing member has a
load-deflection curve which comprises contiguous substantially linear
portions, the stiffness increasing from one portion to the subsequent one
with increased deflection.

13. The valve according to claim 12, wherein the load-deflection curve
has at least three points of stiffness discontinuity.

14. The valve according to claim 11, wherein the ratio of the stiffness
of the biasing member in two contiguous tracts of the load-deflection
curve is comprised between 1.2 and 2.

15. The valve according to claim 1, comprising at least one damper
combined to the biasing member.

16. The valve according to claim 15, wherein: the at least one damper
comprises a seat; the biasing member is at least partly arranged in the
seat; the damper being configured and arranged to contrast radial
expansion of the biasing member.

17. The valve according to claim 15, comprising a first damper and a
second damper arranged at opposite ends of the biasing member.

18. The valve according to claim 17, wherein: each of the first damper
and the second damper comprises a seat; the biasing member is at least
partly arranged in the seat of the first damper and at least partly
arranged in the seat of the second damper; the first damper and the
second damper being configured and arranged to contrast radial expansion
of the biasing member.

19. The valve according to claim 15, wherein the biasing member comprises
at least a first helical spring.

20. The valve according to claim 19, wherein the biasing member comprises
at least a second helical spring.

21. The valve according to claim 19, wherein at least one of the first
and the second helical spring is a linear spring.

22. The valve according to claim 1, wherein the shutter is a ring shutter
resiliently biased by a plurality of non-linear biasing members arranged
along the annular development of the ring shutter.

23. The valve according to claim 1, wherein: the shutter is a poppet
shutter; the valve comprising: at least one shutter guide fixedly
arranged inside the valve body, the poppet shutter being slidingly guided
by the shutter guide; and a flow passage from the flow inlet to the flow
outlet, the flow passage being formed between an inside surface of the
valve body and an outside surface of the shutter guide and of the poppet
shutter, wherein the biasing member is housed in the shutter guide.

24. A differential pressure poppet valve comprising: a valve body, the
valve body having at least one flow inlet and one flow outlet; at least
one shutter guide disposed inside the valve body; at least one poppet
shutter slidingly guided by the shutter guide; a flow passage from the
flow inlet to the flow outlet, the flow passage being formed between an
inside surface of the valve body and an outside surface of the shutter
guide and of the poppet shutter; at least one biasing member configured
to bias the poppet shutter towards a closed position so as to block the
flow passage through the flow inlet; and a surge-suppression arrangement
configured to suppress or mitigate surge phenomena in the biasing member.

25. A reciprocating compressor comprising: a cylinder; a piston slidingly
arranged and reciprocatingly moving in the cylinder; a suction duct and a
discharge duct in fluid communication with the cylinder; at least a
suction valve in the suction duct and a discharge valve in the discharge
duct, wherein opening and closing of the suction valve and the discharge
valve are automatically controlled by a differential pressure across the
valve, and wherein the suction valve and the discharge valve are
differential pressure valves according to claim 1.

26. A method for mitigating or suppressing spring surge in a differential
pressure valve comprising a valve body, the valve body having at least
one flow inlet and one flow outlet, at least one shutter, the shutter
being movable between an open position and a closed position under a
differential across the valve, a flow passage from the flow inlet to the
flow outlet, and at least one biasing member configured to bias the
shutter towards a closed position so as to block the flow passage through
the flow inlet, the method comprising: suppressing propagation of
resonance compression waves in the biasing member by non-linear
deflection of the biasing member.

27. A method for operating a reciprocating compressor, the compressor
comprising a cylinder, a piston sliding in the cylinder, a suction duct
with a suction valve and a discharge duct with a discharge valve, each
valve comprising at least one shutter, the method comprising: providing
for each shutter at least one non-linear biasing member configured to
bias the shutter toward a closed position; reciprocatingly moving the
piston in the cylinder to suck a gas in the cylinder at a suction
pressure and discharge the gas from the cylinder at a discharge pressure;
and selectively opening and closing the suction valve and the discharge
valve by differential pressure across the valves.

28. The method according to claim 27, wherein the compressor is operated
at between 150 and 300 rpm.

29. The method according to claim 27, wherein the discharge pressure is
between 800 and 4500 bar and preferably between 1500 and 3500 bar.

Description:

BACKGROUND OF THE INVENTION

[0001] The embodiments disclosed relate generally to differential pressure
valves, i.e. to valves which are automatically actuated by the pressure
difference across the valve. Some exemplary embodiments specifically
relate to reciprocating compressor valves, such as in particular to
poppet valves or hyper compressors.

[0002] Hyper compressors, those capable of producing gas pressure levels
up to or above 3,000 bars, are widely used in industrial application,
including, but not limited to, the production of low density
polyethylene, or LDPE. The efficient performance of these compressors is
controlled at least in part by suction and discharge automatic poppet
valves. FIG. 1 illustrates a cutaway of a portion of a hyper compressor 2
of the conventional art comprising two poppet valves 10. FIG. 2
illustrates an enlarged section of one of the conventional poppet valves
of the compressor shown in FIG. 1, in an opened position. A poppet guide
according to the state of the art is disclosed in US-A-2010/0024891.

[0003] As shown in FIG. 1, a hyper compressor 2 usually comprises a casing
3 in which a cylinder 4 is formed. A piston rod 5 slides reciprocatingly
in the cylinder 4 to suck a fluid from a suction duct 6 and discharge the
fluid at a higher pressure in a discharge duct 7. A poppet valve 10 is
arranged in each said suction duct 6 and discharge duct 7. In FIG. 1
reference number 10S designates the poppet valve in the suction duct 6
and reference number 10D designates the poppet valve in the discharge
duct 7. Each poppet valve 10S, 10D is designed as shown in FIG. 2 and is
designated 10 therein.

[0004] As shown in FIG. 2, the conventional poppet valve 10 includes a
valve body 11 that contains therein a poppet, or poppet shutter, 12
configured to open and close the gas flow path in and out of the hyper
compressor 1, a spring 14 configured to keep the poppet shutter 12 in a
closed position against a closure seat 13 formed by a portion of the
internal surface of the valve body 11, and a shutter guide 16 that
contains the poppet shutter 12 and the spring 14. As shown, when the
poppet shutter 12 is forced opened, a flow passage 17 (identified by
several arrows in FIG. 2) is formed from a flow inlet 18 to a flow outlet
20 of the conventional poppet valve 10, the flow path being defined by
the space formed between the poppet shutter 12 and the valve body 11 as
well as between the shutter guide 16 and the valve body 11. The shutter
guide 16 of the conventional poppet valve 10 further includes a discharge
opening 22 along an axis A-A of the shutter guide 16 connecting an inside
chamber 26 of the shutter guide 16 to the flow passage 17 in a region of
flow stagnation, the back pressure in the inside chamber 26 being defined
at least in part by the static pressure in the region of the flow passage
17 around the axis A-A of conventional poppet valve 10.

[0005] Opening and closing of the poppet valves 10, 10S, 10D is
automatically controlled by differential pressure across the valves.
These valves are therefore sometime called "automatic valves" and
distinguish over controlled valves, such as those commonly used in
internal combustion engines, where valve opening and closing is
controlled by an external actuator, such by way of a cam shaft.

[0006] The suction poppet valve 10S is arranged such that it opens when
the pressure in the cylinder 4 of the hyper compressor 2 diminishes
during the suction stroke of the piston rod 5. The pressure in the
suction duct 6 overcomes the force of the spring 14; the differential
pressure across the valve causes opening of the valve and fluid is sucked
in the compressor cylinder 4. The discharge valve 10D is closed. Once the
piston rod 5 reaches the bottom dead center, the movement is reversed and
compression of the fluid in the cylinder starts. Increased pressure in
the cylinder 4 automatically closes the suction valve 10S and opens the
discharge valve 10D when the differential pressure across the discharge
valve 10D, between the compressor cylinder 4 and the discharge duct 7,
overcomes the force of the relevant spring.

[0007] At each closing movement the poppet shutter 12 of the relevant
poppet valve 10, 10S, 10D strikes violently against the seat 13 of the
valve body 11 and each opening stroke causes the poppet shutter 12 to
strike against the shutter guide 16.

[0008] These poppet valves play an important role in the reliability of
hyper compressors used in plants for the production of LDPE. The
performance of such valves depends not only on selected material
properties and a suitable design to withstand high operating gas
pressures, but also on a proper dynamic behavior of the poppet shutter
12. The proper opening and closing of the valve are influenced by various
design constraints related to several dynamic forces acting on the valve,
including a drag force acting on the poppet shutter 12 and shutter guide
16 to open the valve, this drag force being generated by the interaction
of the gas flow with the noted valve parts; a gas pressure force acting
on the shutter guide 16 to close the conventional valve 10, this gas
pressure force being generated by the flow back pressure acting on a back
surface of the shutter guide 16; an inertia force associated with the
mass of the poppet shutter 12; and a spring force generated by the spring
14 to close the valve, among others.

[0009] Hyper compressors operate usually in a speed range between 150 and
300 rpm. At each cycle all the valves perform an opening and closing
movement with corresponding impacts of the poppet shutter against the
seat 13 and against the shutter guide 16. Repeated impacts cause impact
wear and frontal damages, which eventually lead to poppet failure. Impact
wear causes material consumption and surface irregularities that can
crate favorite sites for the formation of cracks. These can propagate by
impact fatigue due to the stress waves generated by dynamic loads caused
by impacts, till final fracture of the poppet shutter. In case of high
impact velocities, impact fatigue can nucleate cracks itself, even in the
absence of impact wear.

[0010] When there are impact loads on the springs, the stress propagates
along the spring wire. The end coil of the spring in contact with the
applied load takes up whole of the deflection and then it transmits a
large part of its deflection to the adjacent coils. This wave of
compression travels along the spring indefinitely. Resonance will occur
depending upon time traveled. This results in very large deflections and
correspondingly very high stresses. Under these conditions, it is just
possible that the spring may fail. This phenomenon is called surge. From
another view point, an impact stress applied on the spring upon closing
or opening of the shutter introduces a deformation of the spring
according to a function which can be decomposed in a Fourier series which
also includes harmonics corresponding to the resonance frequencies of the
spring. Under some circumstance this can generate the above mentioned
compression wave traveling along the spring. The high stress induced in
the spring by resonance can eventually result in spring failure. If this
occurs in an automatic valve of a reciprocating compressor the shutter
will continue to operate but under abnormal operating conditions. Impact
velocities of the shutter increase to very high values giving rise to
frontal damage (impact wear and impact fatigue) of the shutter. Frontal
damage generate cracks which rapidly propagate under dynamic stresses
produced by repeated impacts till final failure of the valve, when the
shutter breaks.

[0011] Spring surge can be induced also by gas dynamic forces (vortex
shedding). These forces generate pressure oscillations with a frequency
typically ranging between 100 and 1200 Hz, corresponding to one or more
resonance frequencies of the valve spring.

[0012] Automatic valves are used not only in hyper compressors but also in
other kinds of reciprocating compressors, commonly used for lower
pressure ranges, e.g. between 100 and 1000 bar. These automatic valves
comprise a valve stop with one or more outlet apertures and a valve seat
with one or more inlet apertures. Disk-shaped or ring-shaped shutters, or
valve plates, are arranged between the seat and the counter-seat and are
resiliently urged by springs against the valve seat. Opening and closing
is controlled by the differential pressure across the valve. These valves
are commonly called "ring valves", to indicate the shape of the shutters
used therein. Spring surge can arise also in this kind of automatic
valves of reciprocating compressors, due to the effect of the impact
loads on the spring upon opening and closing of the ring-shaped shutters.

[0013] It would therefore be desirable to develop an improved
reciprocating-compressor valve, in particular an automatic valve, such as
specifically a poppet valve for hyper compressors, where spring surge
phenomena are suppressed or at least mitigated.

BRIEF DESCRIPTION OF THE INVENTION

[0014] By providing a biasing member having a non-linear behavior,
propagation of surge waves along the biasing member is prevented or at
least reduced. Should the shutter be subject to a load which contains a
frequency equal to the resonance frequency of the biasing member, the
latter would tend to resonate with generation of a localized compression
of the biasing member. Since the biasing member is non-linear, the
resonance frequency will change just as a consequence of triggering a
surge wave in the resilient member. Resonating of the biasing member is
thus prevented or at least strongly reduced.

[0015] In general terms the subject matter disclosed herein concerns a
pressure valve, e.g. a differential pressure valve, in particular (but
not exclusively) a reciprocating compressor valve, comprising a valve
body and a shutter as well as a shutter biasing member, wherein opening
and closing of the valve is controlled by differential pressure across
the valve, and wherein a surge-reduction arrangement is provided,
configured to suppress or mitigate surge phenomena in said biasing
member.

[0016] Thus, according to one aspect, a differential pressure valve is
provided, comprising: a valve body, the valve body having at least one
flow inlet and one flow outlet: at least one shutter, the shutter being
movable between an open position and a closed position under a
differential pressure across the valve; at least one flow passage from
the flow inlet to the flow outlet; at least one biasing member configured
to bias the shutter towards a closed position so as to block the flow
passage through the flow inlet; wherein the biasing member is non-linear.

[0017] According to a further aspect, a differential pressure poppet valve
is provided. The differential pressure poppet valve comprises a valve
body, the valve body having at least one flow inlet and one flow outlet;
at least one shutter guide disposed inside the valve body; at least one
poppet shutter slidingly guided by the shutter guide; a flow passage from
the flow inlet to the flow outlet, the flow passage being formed between
an inside surface of the valve body and an outside surface of the shutter
guide and of the poppet shutter; at least one biasing member configured
to bias the poppet shutter towards a closed position so as to block the
flow passage through the flow inlet; and a surge-suppression arrangement
configured to suppress or mitigate surge phenomena in the biasing member.

[0018] According to another aspect, a method for mitigating or suppressing
spring surge in a differential pressure valve is provided. The
differential pressure valve comprises : a valve body, the valve body
having at least one flow inlet and one flow outlet; at least one shutter,
the shutter being movable between an open position and a closed position
under a differential across the valve; a flow passage from the flow inlet
to the flow outlet: and at least one biasing member configured to bias
the shutter towards a closed position so as to block the flow passage
through the flow inlet. The method comprises suppressing propagation of
resonance compression waves in the biasing member by non-linear
deflection of the biasing member.

[0019] According to still a further aspect, a method for operating a
reciprocating compressor is provided. The compressor comprises a
cylinder; a piston sliding in the cylinder; a suction duct with a suction
valve and a discharge duct with a discharge valve, each valve comprising
at least one shutter. The method comprises providing for each shutter at
least one non-linear biasing member configured to bias the shutter toward
a closed position; reciprocatingly moving the piston in the cylinder to
suck a gas in the cylinder at a suction pressure and discharge the gas
from the cylinder at a discharge pressure; and selectively opening and
closing the suction valve and the discharge valve by differential
pressure across the valves.

[0020] In some embodiments the valve is a so-called poppet valve,
comprising at least one poppet shutter and at least one shutter guide, in
which the shutter is slidingly guided during opening and closing movement
thereof. The non-linear biasing member can advantageously be housed in
the shutter guide.

[0021] According to other embodiments the valve is a ring valve, such as
an automatic ring valve for reciprocating compressors. Each ring is
resiliently biased by a plurality of biasing members distributed along
the annular extension of the ring. In general the biasing members are
non-linear. In some embodiments, each biasing member comprises at least
two springs arranged in parallel, e.g. two helical springs. In some
embodiments the two springs of each biasing member can be coaxial.

[0022] According to one embodiment, the biasing member comprises a
non-linear, e.g. a progressive, helical spring or is formed by a single
non-linear helical spring. In some embodiments, the biasing member
comprises a first helical spring and a second helical spring arranged in
parallel. Arranged in parallel means that both springs are subject to the
same deflection. At least one of said first and second helical springs is
non-linear. In advantageous embodiments, both helical springs are
non-linear.

[0023] In some embodiments, the biasing member comprises a so-called
friction spring, or ring spring, comprising a plurality of coaxial
conical faced inner and outer ring elements assembled in a columnar form.
The ring elements can have identical stiffness. In some embodiments, the
ring elements differ by stiffness values.

[0024] According to other embodiments the biasing member comprises a
plurality of coaxially arranged Belleville springs or so-called disc
springs arranged in a columnar form. The coaxially and superposed
Belleville springs can be identical to one another or can differ from one
another, e.g. their characteristic load-deflection curve can be different
from one spring to the other. The stillness of the various disc springs
can be selected based on the desired overall load-deflection
characteristic curve. The curve can be designed to achieve additional
advantages, such as reduction of the impact load and impact wear of the
shutter. For this purpose, in some embodiments the disc springs are
constructed and arranged such that the stiffness of the biasing member
increases with deflection.

[0025] According to some embodiments the biasing member can be combined
with at least one damper. The damper can be made of a suitable
elastomeric material, or composite material, such as a reinforced resin.
In other embodiments the damper can also be made of metal.

[0026] In particularly advantageous embodiments two dampers are arranged
at opposite ends of the biasing member. In some embodiments, the biasing
member can comprise a helical spring or a pair of coaxially arranged
helical springs, the ends of which are housed in opposing seats of
respective dampers. The dampers are constructed and arranged to prevent
or limit a radial outward deflection of the resilient member. This causes
the friction to increase when the compressive deflection increases, which
results in surge mitigation or suppression. This results in a
modification of the characteristic of the biasing member. Interaction
between the spring and the damper(s) due to radial deflection causes on
the one hand energy dissipation and on the other alters the resonance
frequency of the spring. Both factors contribute to surge suppression or
mitigation. The spring becomes non linear due to the spring-damper
interaction.

[0027] In other embodiments the dampers are arranged to contact the inner
surface of the springs. The interaction between damper and spring in this
cases reduces with increasing deflection of the spring, since radial
expansion reduces the contact force between the inner surface of the
spring and the damper. Also in this case the result is a change in the
dynamic behavior of the spring, i.e. a non-linear behavior of the spring.

[0028] The modification on the damper/spring interaction due to radial
spring deflection modifies the resonance frequency of the spring.
Consequently, if a surge compression wave starts to propagate along the
spring, once the wave achieves one end of the spring the spring
deflection will alter the springy/damper contact forces and modify
automatically the resonance frequency of the spring, resulting in surge
reduction or suppression.

[0029] According to further aspect, the subject matter disclosed herein
concerns a reciprocating compressor comprising a cylinder; a piston
slidingly arranged and reciprocatingly moving in said cylinder; a suction
duct and a discharge duct in fluid communication with said cylinder; at
least a suction valve in said suction duct and a discharge valve in said
discharge duct; opening and closing of said suction valve and said
discharge valve being automatically controlled by a differential pressure
across the valve. One or both suction and discharge valves are comprised
of a shutter and a biasing member having a non-linear characteristic
load-deflection curve.

[0030] In some embodiments the compressor is a hyper compressor. In some
exemplary embodiments the compressor rotates at between 150 and 300 rpm,
i.e. the piston performs 150-300 cycles per minute. Consequently each
suction and discharge valve in the compressor perform 150-300 opening and
closing cycles per minute. According to some embodiments the compressor
operates at a discharge pressure between 800 and 4500 bar, for example
between 1500 and 3500 bar.

[0031] According to still a further aspect, the subject matter disclosed
herein concerns a method for mitigating or suppressing spring surge in a
reciprocating compressor valve, comprising the step of using a non-linear
biasing member acting on the valve shutter. The non-linearity behavior of
the biasing member prevents or reduces resonance compression waves from
propagating along the biasing member.

[0032] The above brief description sets forth features of the various
embodiments of the present invention in order that the detailed
description that follows may be better understood and in order that the
present contributions to the art may be better appreciated. There are, of
course, other features of the invention that will be described
hereinafter and which will be set forth in the appended claims. In this
respect, before explaining several embodiments of the invention in
details, it is understood that the various embodiments of the invention
are not limited in their application to the details of the construction
and to the arrangements of the components set forth in the following
description or illustrated in the drawings. The invention is capable of
other embodiments and of being practiced and carried out in various ways.
Also, it is to be understood that the phraseology and terminology
employed herein are for the purpose of description and should not be
regarded as limiting.

[0033] As such, those skilled in the art will appreciate that the
conception, upon which the disclosure is based, may readily be utilized
as a basis for designing other structures, methods, and/or systems for
carrying out the several purposes of the present invention. It is
important, therefore, that the claims be regarded as including such
equivalent constructions insofar as they do not depart from the spirit
and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A more complete appreciation of the disclosed embodiments of the
invention and many of the attendant advantages thereof will be readily
obtained as the same becomes better understood by reference to the
following detailed description when considered in connection with the
accompanying drawings, wherein:

[0035]FIG. 1 shows a section of a portion of a reciprocating hyper
compressor according to the state of the art;

[0036]FIG. 2 illustrates a section along a longitudinal axis of a poppet
valve for a hyper compressor according to the state of the art:

[0037]FIG. 3 illustrates a longitudinal section of a portion of a hyper
compressor according to an exemplary embodiment;

[0038] FIG. 4 illustrates a longitudinal section of a poppet valve in an
opened position according to an exemplary embodiment:.

[0039] FIG. 4A illustrates a side view of the progressive spring of the
valve of FIG. 4;

[0040] FIGS. 4B and 4C illustrate diagrams showing the characteristics of
the progressive spring used in the embodiment of FIG. 4;

[0041] FIG. 5 illustrates a longitudinal section of a poppet valve in an
opened position according to another exemplary embodiment;

[0042] FIG. 6 illustrates a longitudinal section of a poppet valve in an
opened position according to yet another exemplary embodiment, using ring
springs;

[0043] FIG. 6A illustrates an enlargement of the biasing member of the
valve of FIG. 6;

[0044]FIG. 7 illustrates a longitudinal section of a poppet valve in an
opened position according to a further exemplary embodiment, using
Belleville springs:

[0048]FIG. 11 illustrates a further exemplary embodiment of a Belleville
spring arrangement;

[0049]FIG. 12 illustrates a longitudinal section of a poppet valve using
a hybrid spring combination:

[0050] FIG. 13 illustrates a longitudinal section of a poppet valve
according to a further exemplary embodiment including a Belleville spring
arrangement in parallel to a helical spring;

[0051] FIGS. 14 and 15 illustrate a longitudinal section of a poppet valve
in an opened position according to additional further exemplary
embodiments of the invention;

[0052] FIG. 16 illustrates a longitudinal section of a ring valve with
non-linear resilient members according to a further embodiment, according
to line XVI-XVI in FIG. 16A;

[0053] FIG. 16A illustrates a view according to line XVIA-XVIA of FIG. 16;

[0054]FIG. 17 illustrates an enlargement of the detail XVII in FIG. 16.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION

[0055] The following detailed description of the exemplary embodiments
refers to the accompanying drawings. The same reference numbers in
different drawings identify the same or similar elements. Additionally,
the drawings are not necessarily drawn to scale. Also, the following
detailed description does not limit the invention. Instead, the scope of
the invention is defined by the appended claims.

[0056] Reference throughout the specification to "one embodiment" or "an
embodiment" or "some embodiments" means that the particular feature,
structure or characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter disclosed.
Thus, the appearance of the phrase "in one embodiment" or "in an
embodiment" or "in some embodiments" in various places throughout the
specification is not necessarily referring to the same embodiment(s).
Further, the particular features, structures or characteristics may be
combined in any suitable manner in one or more embodiments.

[0057] The following detailed description refers to single poppet valves.
It shall however be understood that at least some of the features
disclosed herein could be embodied in a multi-poppet valve, i.e. a valve
including more than one shutter and relevant shutter guide. For example a
valve stop including a plurality of guides for a plurality of poppet
shutters can be used in combination with a valve seat with a plurality of
suction openings, each corresponding to a respective poppet shutter.

[0058] Referring first to FIG. 3, the general structure of a hyper
compressor will be described, limited to those parts which are important
for an understanding of embodiments of the invention. The hyper
compressor 102 comprises a casing 103 in which a cylinder 104 is formed.
A piston rod 105 slides reciprocatingly in the cylinder 104 to suck a
fluid from at least one suction duct 106 and discharge the fluid at a
higher pressure in at least one discharge duct 107. A respective poppet
valve is arranged in each said suction duct 106 and discharge duct 107
respectively. Reference number 110S designates the poppet valve in the
suction duct 106 and reference number 110D designates the poppet valve in
the discharge duct 107. The arrangement of the suction duct and the
discharge duct with respect to the cylinder 104 can be different from
that shown in the drawings. In particular, the position of the valve axes
with respect to the cylinder axis can be different and can depend upon
the design values of the inlet and outlet pressure of the hyper
compressor.

[0059] The piston rod 105 is actuated by a crank (not shown). In some
embodiments the rotary speed of the crank is in the range between 150 and
300 rpm, i.e. the piston rod 105 performs a complete compression-suction
movement 150-300 times/minute. Consequently, each valve 110S, 110D
performs an opening-closing movement between 150 and 300 times/minute.
The discharge pressure of the compressor ranges between 800 and 4000 bar,
for example between 1500 and 3500 bar.

[0060] Each poppet valve 110S, 110D can be designed as illustrated in the
exemplary embodiment shown in FIG. 4, where the poppet valve is
designated 110 as a whole and is shown in its open position, allowing gas
to flow through the valve from the inlet toward the out let.

[0061] The poppet valve 110 includes a valve body 111 having a valve axis
A-A, a poppet shutter 112, a biasing member 114 and a shutter guide 116.
In the exemplary embodiment shown in FIG. 4 the biasing member 114
comprises a helical compression spring. Different biasing members can be
used, instead, as will be discussed later on, reference being made to the
remaining figures of the drawings. In some embodiments the poppet shutter
112 has an inner cavity 113 wherein a spacer 115 is disposed. The spring
114 is housed partly in the inner cavity 113 of the poppet shutter 112
and partly in an inner chamber 117 of the shutter guide 116. More
specifically, the spring 114 is retained between the spacer 115 and a
bottom surface 117B of the inner chamber 117 of the shutter guide 116.
The surface 117A of the inner chamber 117 is in sliding contact with the
outer surface 112A of the poppet shutter 112, such that the latter is
slidingly guided by the shutter guide 116 during opening and closing
movement of the poppet shutter 112.

[0062] The poppet valve 110 also includes a flow inlet 118 and a flow
outlet 120. In operation, the spring 114 biases the shutter 112 away from
the shutter guide 116 in a closed position where a portion 122 of a
surface of the shutter 112 rests against a closure seat 124 formed by a
surface portion of the valve body 111, thereby preventing gas from
flowing from the flow inlet 118 to the flow outlet 120 or vice versa. The
spring 114 is suitably pre-loaded to provide sufficient closure pressure
between the shutter 112 and the closure seat 124. When the force exerted
on the shutter 112 by the differential gas pressure across the valve is
higher than the biasing force of the spring 114, the shutter 112 is moved
to the opened position shown in FIG. 4, thereby allowing gases to flow
from the flow inlet 118 to the flow outlet 120 through flow passages 126
formed between the shutter 112 and an inner surface of the valve body 111
as well as between the shutter guide 116 and the inner surface of the
valve body 111, as illustrated by the arrows 128 in FIG. 4.

[0063] In the embodiment shown in FIG. 4 the spring 114 is a helical
spring or coil spring. Differently from poppet valves of the prior art,
however, the spring 114 is not a linear spring but rather a non-linear
spring, e.g. a progressive spring. In general terms, a progressive
non-linear helical spring can be schematically represented by an
arrangement of serially positioned springs having a variable stiffness.
In general terms, such an arrangement can be obtained in different
manners. In the embodiment shown in FIGS. 4 and 4A this is achieved by a
helical spring wherein the pitch between the coils forming the spring
varies along the axial extension of the spring, as best seen in the
enlargement of FIG. 4A. In the latter the pitches, i.e. the spacing
between two adjacent active coils forming the spring 114 are labeled P1,
P2, P3, . . . Pn-1, Pn. The pitch can vary stepwise from one end to the
opposite end of the spring, though this is not mandatory; for example the
pitch can decrease from each spring end towards the spring center or
vice-versa.

[0064] The non-linear, progressive helical spring behavior suppresses or
reduces surge phenomena as follows. Theoretically, in a common linear
helical spring the total spring deflection is distributed uniformly among
the various coils. This means that the distance between each pair of
adjacent coils reduces to an identical extent until finally the coils
contact each other. In the progressive helical spring the coils which are
distanced by the smallest pitch will touch each other earlier than the
remaining coils. Once two adjacent coils contact each other, they do not
deflect further and subsequent deflection of the spring will be
distributed among the remaining, non-contacting coils. This changes the
stiffness of the coil. While compressive deflection increases, a
progressively larger number of coils contact each other causing a gradual
stiffness increase of the spring, until finally the maximum compressive
deflection is achieved with each coil contacting the adjacent ones. FIG.
4B shows a load (L) vs. deflection (D) diagram of an exemplary non-linear
progressive helical spring. The characteristic curve is composed by a
sequence of straight portions having an increasing inclination over the
abscissa. D1, D2, D3 and D4 indicate deflection
values at which a pair of adjacent coils get in contact due to spring
deflection. The derivative of the curve represents the stiffness of the
spring. The stiffness increases with increasing deflection. FIG. 4C
represents the trend of the stiffness (K) as a function of the spring
deflection (D). K1, K2, K3, K4 are the progressively
increasing stiffness values of the spring 114.

[0065] The spring 114 is pre-loaded and the overall deflection is
determined by the stroke performed by the poppet shutter 112 when moving
from the closed position to the opened position.

[0066] The valve can be designed such that under normal operative
conditions the minimum and maximum spring deflections are lower than
D1. In this case, referring to FIG. 4B the value d1 on the
abscissa represents the deflection of spring 114 in the pre-loaded
condition (valve closed) and d2 represents the maximum deflection of
the spring 114 when the poppet shutter is open, in the case of absence of
surge phenomena. Under these operative conditions the spring will have a
normal linear behavior and will never exceed a deflection which causes
mutual contact of adjacent spring coils if no surge phenomena arise. Such
operating conditions preserve the spring from inter-coil wear.

[0067] According to other embodiments the valve can be designed such that
under normal operating conditions the spring deflection exceeds the first
value D1 and therefore during normal valve operation the spring
stiffness varies. In this case, for example, the pre-load deflection
(poppet shutter 112 closed) will be d2 and the maximum deflection
(poppet shutter 112 open) will be d3. Inter-coil contact and
moderate inter-coil wear can occur. However, the valve behavior will be
improved from the point of view of dynamic stresses, because the
increased spring stiffness from K1 to K2 during the opening
stroke will reduce the impact speed of the poppet shutter 112 upon
opening of the valve. This will reduce frontal damages and dynamic
fatigue stresses of the valve.

[0068] In case of surge, the compression wave will be prevented from
traveling along the spring due to the non-linear increase of the spring
stiffness. Since the stiffness of the progressive spring varies with
deflection, the resonance frequency thereof also varies and propagation
of compressive waves (spring surge) is suppressed or at least strongly
reduced. The stiffness change and resonance frequency change due to
progressive, non-linear characteristic of the spring, causes suppression
of the propagation of the surge compressive wave.

[0069] FIG. 5 illustrates a further exemplary embodiment of the invention.
In this embodiment, the general structure of the valve is substantially
the same as in FIG. 4 and will not be described in detail again. The
poppet valve of FIG. 5 differs from the poppet valve of FIG. 4 because
the biasing member 114 comprises two helical springs 114A and 114B in
parallel, arranged one inside the other. More specifically, the spring
114A has a larger diameter and is arranged around the smaller spring
114B. The spacer 115 is somewhat differently shaped with respect to the
spacer 115 in FIG. 4 to provide sufficient space for the inner spring
114B.

[0070] According to some embodiments, at least one of the two springs
114A, 114B is a non-linear spring, e.g. a progressive spring. In some
embodiments both springs 114A. 114B are non-linear springs, e.g.
progressive springs. As described with respect to FIG. 4, also in the
embodiment of FIG. 5 the non-linear behavior of the spring causes surge
suppression or surge reduction. Both springs 114A and 114B are suitably
pre-loaded.

[0071] In some embodiments the springs 114A, 114B are designed such that
at least the first resonance frequency (first harmonic) of one of said
springs 114A, 114B is different from the first resonance frequency (first
harmonic) of the other spring. In some embodiments also at least the
frequencies of the second and preferably also of the third and possibly
fourth order (second, third, fourth harmonic) are different for the two
springs 114A, 114B. For example, if a first spring has a first resonant
frequency at 100 Hz and subsequent resonant frequencies at 200, 300, 400
Hz, it is suitable to design the second spring such that neither the
first nor the second, third and fourth resonant frequencies thereof are
at 100, 200, 300 or 400 Hz.

[0072] FIGS. 6 and 6A illustrate a further embodiment of the invention.
The overall structure of the valve 110 is substantially similar to the
structure of the valve illustrated in FIGS. 4 and 5. In the embodiment of
FIG. 6, however, the biasing member 114 is in the form of a so-called
friction spring or ring spring. The friction spring comprises a plurality
of elastic ring elements arranged in series and coaxial to one another,
in a columnar arrangement. More specifically, the biasing member 114
comprises at least one tension ring element 114X and at least one
compression ring element 114Y. In the example shown in FIG. 6, actually a
plurality of tension ring elements 114X are combined with a plurality of
compression ring elements 114Y. The compression ring elements and tension
ring elements are arranged in an alternating manner, a tension ring
element 114X following a compression ring element 114Y and so on.
Mutually adjacent ring elements are in contact with one another at
contacting frustum-conical friction surfaces 114Sx and 114Sy, as best
shown in the enlargement of FIG. 6A.

[0073] When an axial load is applied to the ring spring 114, the tension
ring elements 114X deflect radially outwardly, while the compression ring
elements 114Y deflect radially inwardly. Friction is generated at the
frustum-conical surfaces of mutual contact 114Sx and 114Sy. The behavior
of the ring spring 114, i.e the load-deflection curve thereof is
non-linear. In addition, the friction at the frustum-conical friction
surfaces 114Sx, 114Sy generates a damping died. Both factors mitigate or
suppress surge phenomena which may arise during operation of the valve.

[0074] The behavior of the ring spring is non-linear per se and
self-dampening. As noted, both features contribute to spring surge
reduction or suppression. In some embodiments, an additional
non-linearity factor can be introduced by varying the stiffness of the
ring elements 114X, 114Y forming the ring spring or friction spring 114.
In some embodiments ring elements with variable stiffness are used to
obtain a more advantageous load-deflection curve as will be discussed in
more detail here below.

[0075]FIG. 7 illustrates a longitudinal section of a poppet valve in a
further embodiment. The valve is shown in the open position. The overall
structure of the valve is similar to that already described in detail in
connection with FIG. 4 and will not be described again. The valve 110 of
FIG. 7 differs from the valve of FIG. 4 mainly because the biasing member
114 is formed by a series of disc springs, also known as Belleville
springs, in a columnar arrangement, each spring being designated 114Z.
Each disc spring 114Z is formed by a conically shaped resilient disc
element. In some embodiments the Belleville springs are solid. In other
embodiments slotted Belleville springs can be used. It is also possible
to combine slotted and non-slotted disc springs in the same set of
Belleville springs, e.g. to obtain a desired load-deflection curve of the
springs set.

[0076] Belleville springs are non-linear. Their stiffness varies with the
degree of deflection. Additionally, a biasing member formed by a
plurality of superposed Belleville springs is self-damping. Adjacent and
superposed Belleville springs are in contact along friction contacting
surfaces. Deformation of the springs under load generates friction
between contacting surfaces with a consequent damping effect.

[0077] A non-linear behavior of the biasing member formed by the set of
Belleville springs 114Z contributes to spring surge suppression or
mitigation since the compression wave cannot propagate along the series
of springs 114Z as stiffness and resonance frequency vary with
deflection. As noted above with respect to non-linear, progressive
helical springs, as well as in the case of friction springs, also in the
case of a plurality of Belleville or disc springs the compression wave
triggered by surge is prevented from propagating along the biasing member
due to the instant change in resonance frequency caused by the stiffness
modification. Moreover, the self damping feature of the springs
additionally contributes to surge suppression or reduction.

[0078] The load-deformation characteristic of a set of Belleville springs
can be adapted according to needs, e.g. using Belleville springs 114Z
having different stiffness values and/or by suitably orienting the
springs. FIGS. 8(A) an 8(B) illustrate two different trends of a
load-deflection curve of different Belleville spring sets 114. Load is
plotted on the vertical axis and deflection is plotted on the abscissa.
In FIG. 8(A) the spring set is characterized by a decreasing stiffness
with increasing deflection. In FIG. 8(B) the spring stiffness increases
when the deflection increases. This last spring behavior is currently
preferred in some circumstances, because a reduction of impact stress and
consequent impact damage is achieved.

[0079] An increasing stiffness is a generally desirable feature also when
a different kind of non-linear spring, e.g. a ring-spring or friction
spring, or a non-linear helical spring is used.

[0080] Similar force-deformation curves can be obtained also by means of a
ring-spring as shown in FIGS. 6, 6A, when rings of variable stiffness are
used in combination.

[0081] In some embodiments increasing stiffness of the columnar
arrangement of Belleville springs can be obtained by suitable selection
and design of the various springs. FIG. 9A schematically illustrates a
possible arrangement of Belleville springs designed to achieve an
increasing stiffness of the resilient member formed by the springs. FIG.
9B diagrammatically illustrates the characteristic curve of the spring
assembly of FIG. 9A. The Belleville springs 114Z of FIG. 9A have a
variable thickness. The spring thickness increases from a first portion x
to a second portion y and from said second portion v to a third portion
z. When the load applied on the spring increases, all springs in the
x-portion will deflect to a larger extent and will first become flat
(condition of maximum deflection). This causes stiffness increase:
further deflection due to load increase will be concentrated on the
springs of the y- and z-portions only. The springs of the y-portion will
reach maximum deflection first and therefore continued load increase will
cause deflection of only the remaining springs in the z-portion of the
Belleville spring pack. An additional stiffness increase is thus
obtained. In FIG. 9B the characteristic curve has three sections labeled
x+y+z, v+z and z respectively. In the first section all three portions x,
y and z will contribute to deflection, in the y+z section only the
springs in the y- and z-portion will deflect. Finally, in the z-section
the spring stiffness increases further and only the springs in the
z-portion will deflect. Each section of the curve is approximately
linear, but the overall trend of the characteristic curve has an
increasing steepness due to increased stiffness of the spring
arrangement.

[0082]FIG. 10A shows a different embodiment of a Belleville spring
arrangement which has a similar behavior. FIG. 10B shows the
corresponding characteristic curve. Same references indicates
corresponding features as in FIGS. 9A, 9B. While in FIG. 9A variable
stiffness is obtained with Belleville springs of variable thickness, in
FIG. 10A variable stiffness is obtained by arranging a different number
of Belleville springs in parallel in each portion of the Belleville
spring column.

[0083] Similar results can be achieved by using identical Belleville
springs but interposing there between spacer rings 114R of variable
height, as shown in FIG. 11. The deformation of the springs beyond a
given extent is prevented by the springs abutting against the
corresponding interposed spacer ring 114R. Since the height of the spacer
rings 114R is variable, the degree of free deflection for the various
Belleville springs is not identical. A non-linear behavior is obtained.

[0084] In some embodiments, non-linearity can be achieved also using a
combination of different kinds of springs arranged in series or in
parallel, e.g. a helical spring combined with one or more Belleville
springs, or else a combination of Belleville and ring springs, or a
combination of ring springs and Belleville springs.

[0085]FIG. 12 schematically shows an exemplary embodiment of a poppet
valve comprising a biasing member 114 formed by combined helical spring
114A in series with a set of serially arranged Belleville springs 114Z.
The helical spring can be a non-linear, progressive spring.

[0086] FIG. 13 illustrates an embodiment of a poppet valve comprising a
biasing member 114 comprised of a helical spring 114A in parallel to a
set of Belleville springs 114Z. The helical spring 114A can be a linear
spring or a non-linear, progressive spring. The Belleville springs 114Z
can be arranged for example to obtain a non-linear spring as disclosed in
connection with FIGS. 7, 8, 9, 10 or 11.

[0087] When a resilient member is used, which has an increasing stiffness,
such as e.g. a progressive helical spring (FIGS. 4-4C) or a non-linear
set of Belleville springs (FIGS. 7-11) or a combination thereof, the
springs can be designed such that the stiffness increases stepwise by at
least three different steps, i.e. such that the load-deflection curve has
at least two knick points where the steepness of the curve varies with a
discontinuity of the derivative thereof in the deflection range involved.
The discontinuity corresponds to a stiffness change of the spring.
Moreover, in some embodiments the ratio between two subsequent stiffness
values is preferably comprised between 1.2 and 2, i.e.

1.2<Ki/Ki-121 2

where Ki and Ki-1 are subsequent stiffness values of the
spring.

[0088] According to a further embodiment, surge mitigation or suppression
can be achieved by a combination of a biasing member and a damper
arrangement. FIG. 14 illustrates a poppet valve 110 with a biasing member
114 combined to a damper arrangement. The valve 110 of FIG. 14 differs
from valve 110 in FIG. 4 because the biasing member 114, in this case
again a helical spring, is combined with two damper members 121, 123. The
damper member 123 replaces the spacer 115. Each damper member 121 and 123
is generally cup-shaped and forms a seat for a respective end portion of
the helical spring 114. Reference 121 A indicates the seat formed by
damper member 121, housing a lower portion of the helical spring 114 and
reference 123A indicates the seat formed by the damper member 123,
housing the upper portion of the helical spring 114. The helical spring
114 can be a linear spring or else a non-linear, progressive spring.

[0089] When subject to compressive load the helical spring deforms axially
but also radially. The axial extension is reduced and the coils tend to
deform radially outwardly. In some embodiments each seat 121A, 121B is
designed such that some degree of clearance exists between the spring
coils and the inner surface of each seat 121A, 121B. The spring can
freely deflect radially outwardly to some extent when axially compressed
without interfering with the seats 121A, 121B of the damper members 121,
123. Beyond a certain axial deflection, however, the increase of the
radial dimension of the coils is such that the coils contact the inner
surfaces of the seats 121A, 121B. Further progressive deflection causes
friction between the spring coils and the seats 121A, 123A of the damper
members 121, 123. The damper members 121, 123 can be made of elastically
deformable material with a high coefficient of friction, e.g. an
elastomeric material or a composite material, which will elastically
oppose the radial outward deflection of the spring coils and generate
friction opposing further axial compression of the spring. In other
embodiments metallic dampers can also be used. 100901 A damping effect is
thus obtained. A deformation wave induced by surge causes a local
deflection of the spring, which goes beyond normal deflection under
correct operation under design conditions. Such deformation is opposed by
the damper members 121, 123. Friction causes energy dissipation and also
a change in the resonance frequency of the spring. The propagation of the
compression wave caused by surge is hindered or suppressed.

[0090] In some embodiments, initial clearance between the coils of spring
114 and inner surfaces of the seats 121A, 123A of the damper members 121,
123 can be dispensed with. In this case the damper members 121, 123 will
oppose radial and thus axial deformation of the spring 114 also when no
surging phenomena are present. In such case tolerances in the
manufacturing of the damper members 121, 123 are less stringent but the
valve will be subject to energy losses, which will result in a reduction
of the compressor efficiency. The friction effect increases due to radial
expansion of the coils and consequent increased interference between the
coils and the side walls of the damper seats 121A, 123A.

[0091] Damper members can be used also in combination with other kinds of
springs, e.g. Belleville springs, to combine the damping action of the
damper member with the intrinsic non-linear behavior and intrinsic
damping action of such kind of springs.

[0092] In some embodiments, more than just one helical spring can be used
in combination with one or more damper members. FIG. 15 illustrates an
exemplary embodiment where two helical springs in parallel are combined
with two damper members. The same reference numbers are used to indicate
the same or similar elements as in the previous embodiments, and
specifically the embodiment of FIG. 14. The biasing member comprises a
first helical spring 114A and a second helical spring 114B. In some
embodiments, the helical spring 114B has coils with an outer diameter
smaller than the inner diameter of the coils of the spring 114A, such
that helical spring 114B is arranged inside helical spring 114A without
mutual contact there between. In some embodiment one, the other or both
of said springs 114A, 114B can be a non-linear, progressive spring as
disclosed in connection to FIGS. 4, 4A. The two springs 114A, 114B have
usually different resonance frequencies and different stiffness values.

[0093] Each damper member 121. 123 is provided with respective two seats
for the two springs 114A, 114B. More specifically the damper member 121
comprises an outer annular seat 121A in which terminal coils of outer
helical spring 114A are housed. The damper member 121 further comprises a
cylindrical seat 121B, coaxial to seat 121A, in which terminal coils of
the inner helical spring 114B are housed. Similarly, the damper member
123 comprises an outer annular seat 123A for the end coils of the helical
spring 114A, and an inner cylindrical seat 123B where the end coils of
the inner helical spring 114B are housed.

[0094] In some embodiments each seat 121A, 121B, 123A, 123B and the
relevant helical springs 114A, 114B are designed such that an initial
clearance is maintained between the coils of each helical spring 114A,
1148 and the inner surfaces of the corresponding seats 121A, 121B, 123A,
123B. The clearance can be such that in case surge phenomena arise, the
radial outward deflection of the spring coils causes interference between
the spring coils and the seats. This generates friction and dissipates
energy, and additionally modifies the resonance frequency of the spring
arrangement, thus preventing or opposing propagation of the compression
wave and eventually suppress or mitigate surge phenomena. The use of
non-linear helical springs 114A, 114B or at least one non-linear spring
will further reduce surge phenomena. Using two springs 114A, 114B having
different resonance frequencies additionally contributes to surge
suppression.

[0095] According to other embodiments the valve is a ring valve, such as
an automatic ring valve for reciprocating compressors. Each ring is
resiliently biased by a plurality of biasing members distributed along
the annular extension of the ring. In general the biasing members are
non-linear. In some embodiments, each biasing member comprises at least
two springs arranged in parallel, e.g. two helical springs. In some
embodiments the two springs of each biasing member can be coaxial.

[0096] FIGS. 16, 16A and 17 illustrate a further embodiment in the form of
a ring valve. In this embodiment, a ring valve is designated 201 as a
whole. The valve 201 comprises a valve body comprised of a valve stop
203, provided with annular through passages 205, and a valve seat 207
provided with annular through passages 209. Shutters in the form of
concentrically disposed sealing rings 212 are arranged between the stop
203 and the seat 205. Each ring 212 is resiliently biased against the
seat 207 by a plurality of biasing members 214 disposed along the annular
development of the ring. Each biasing member 214 is housed in a housing
213 formed in the valve stop 203. According to some embodiments (see in
particular FIG. 17) each biasing member 214 comprises at least two
springs 214A. 214B. Each spring 214A, 214B can be a helical spring. In
the embodiment disclosed in the drawings the springs 214A, 2148 are
coaxial, i.e. the smaller one is arranged in the empty space formed by
the larger one of said springs. In some embodiments both springs 214A,
214B are linear helical springs. In alternative embodiments, one or both
helical springs are non-linear, e.g. progressive springs. In other
embodiments, not shown, each biasing member 114 can comprise more than
two springs. In further embodiments, each biasing member 114 can comprise
a set of Belleville springs 114Z or a combination of helical springs 114A
and Belleville springs 114Z in series or in parallel. In further
embodiments ring springs can be used, alone or in combination with
helical or Belleville springs.

[0097] While the disclosed embodiments of the subject matter described
herein have been shown in the drawings and fully described above with
particularity and detail in connection with several exemplary
embodiments, it will be apparent to those of ordinary skill in the art
that many modifications, changes, and omissions are possible without
materially departing from the novel teachings, the principles and
concepts set forth herein, and advantages of the subject matter recited
in the appended claims. Hence, the proper scope of the disclosed
innovations should be determined only by the broadest interpretation of
the appended claims so as to encompass all such modifications, changes,
and omissions. In addition, the order or sequence of any process or
method steps may be varied or re-sequenced according to alternative
embodiments.